Bending a workpiece of a thin sheet mainly of a metal sometimes results in formation of a camber along the bending ridge line. While leveling will be carried out by means of a device referred to as a leveler in a case where the degree of the camber exceeds a tolerable range, some workpieces, depending on shapes after bending, cannot pass through the leveler, or, even if they can pass through the leveler, requires a special die incorporated in the leveler. This is a factor that will decrease precision of the products or reduce productivity to a great extent.
The Patent Literatures 1-3 disclose related arts.